使用构造函数锁定会导致空引用吗?
所以我今天遇到了一个奇怪的问题——我在锁的临界区内简单地创建了一个实例,当我手动拖动下一行执行时,它会抛出空引用异常。为了说明:
public class SearchEngineOptimizationParser
{
protected static ConcurrentDictionary<string, SearchEngineOptimizationInfo> _referralInformation = null;
protected static DateTime _lastRecordingDate;
protected static object _lockRecordingObject = new object();
protected static Dictionary<string, string> _searchProviderLookups = null;
static SearchEngineOptimizationParser()
{
_referralInformation = new ConcurrentDictionary<string, SearchEngineOptimizationInfo>();
_lastRecordingDate = DateTime.Now;
_searchProviderLookups = new Dictionary<string, string>();
_searchProviderLookups.Add("google.com", "q");
_searchProviderLookups.Add("yahoo.com", "p");
_searchProviderLookups.Add("bing.com", "q");
}
public SearchEngineOptimizationParser()
{
}
public virtual void ParseReferrer(Uri requestUrl, NameValueCollection serverVariables, ISession session)
{
string corePath = requestUrl.PathAndQuery.SmartSplit('?')[0].ToLower();
string referrer = serverVariables["HTTP_REFERER"];
if (!string.IsNullOrWhiteSpace(referrer))
{
NameValueCollection queryString = HttpUtility.ParseQueryString(referrer);
string dictionaryKey = session.AffiliateID + "|" + corePath;
foreach (var searchProvider in _searchProviderLookups)
{
if (referrer.Contains(searchProvider.Key))
{
if (queryString[searchProvider.Value] != null)
{
string keywords = queryString[searchProvider.Value];
SearchEngineOptimizationInfo info = new SearchEngineOptimizationInfo
{
Count = 1,
CorePath = corePath,
AffiliateId = session.AffiliateID,
Keywords = keywords
};
_referralInformation.AddOrUpdate(dictionaryKey, info, (key, oldValue) =>
{
oldValue.Count++;
return oldValue;
});
break;
}
}
}
}
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
lock (_lockRecordingObject)
{
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
SearchEngineKeywordRepository repository = new SearchEngineKeywordRepository();
List<KeyValuePair<string, SearchEngineOptimizationInfo>> currentInfo = _referralInformation.ToList();
Action logData = () =>
{
foreach (var item in currentInfo)
repository.LogKeyword(item.Value);
};
Thread logThread = new Thread(new ThreadStart(logData));
logThread.Start();
_lastRecordingDate = DateTime.Now;
_referralInformation.Clear();
}
}
}
}
编辑:更新的真实对象
public class SearchEngineKeywordRepository
{
public virtual void LogKeyword(SearchEngineOptimizationInfo keywordInfo)
{
LogSearchEngineKeywords procedure = new LogSearchEngineKeywords();
procedure.Execute(keywordInfo.CorePath, keywordInfo.AffiliateId, keywordInfo.Keywords, keywordInfo.Count);
}
}
一般模式是我只想每小时执行此“操作”(在获得大量流量的网站应用程序的上下文中)。我将断点第一个 if 语句,然后单步执行下一行以在第二个 if 语句内执行。这样做时,初始化 SomeObject
实例的行为将导致空引用异常。它有一个完全 100% 默认的构造函数 - 我什至没有指定一个。
然而,当我让代码自然地通过时,它会毫无问题地执行。由于某种原因,当我跳过锁定调用进入关键部分以测试运行该代码时,它似乎导致了各种错误。
我很想知道这是为什么;我知道 lock
关键字只是 Monitor.Enter(o)
try / finally 块的语法糖,但这似乎是在调用构造函数时,还有其他东西正在发生。
有人有什么想法吗?
编辑:我已经添加了实际的代码。我可以随意重现这一点,但我仍然不明白为什么会发生这种情况。我尝试将此代码复制到另一个解决方案,但问题似乎没有发生。
So I encountered a strange issue today - I had a simple creation of an instance inside the critical section of a lock, and it would throw a null reference exception when I manually dragged the next line to execute. To illustrate:
public class SearchEngineOptimizationParser
{
protected static ConcurrentDictionary<string, SearchEngineOptimizationInfo> _referralInformation = null;
protected static DateTime _lastRecordingDate;
protected static object _lockRecordingObject = new object();
protected static Dictionary<string, string> _searchProviderLookups = null;
static SearchEngineOptimizationParser()
{
_referralInformation = new ConcurrentDictionary<string, SearchEngineOptimizationInfo>();
_lastRecordingDate = DateTime.Now;
_searchProviderLookups = new Dictionary<string, string>();
_searchProviderLookups.Add("google.com", "q");
_searchProviderLookups.Add("yahoo.com", "p");
_searchProviderLookups.Add("bing.com", "q");
}
public SearchEngineOptimizationParser()
{
}
public virtual void ParseReferrer(Uri requestUrl, NameValueCollection serverVariables, ISession session)
{
string corePath = requestUrl.PathAndQuery.SmartSplit('?')[0].ToLower();
string referrer = serverVariables["HTTP_REFERER"];
if (!string.IsNullOrWhiteSpace(referrer))
{
NameValueCollection queryString = HttpUtility.ParseQueryString(referrer);
string dictionaryKey = session.AffiliateID + "|" + corePath;
foreach (var searchProvider in _searchProviderLookups)
{
if (referrer.Contains(searchProvider.Key))
{
if (queryString[searchProvider.Value] != null)
{
string keywords = queryString[searchProvider.Value];
SearchEngineOptimizationInfo info = new SearchEngineOptimizationInfo
{
Count = 1,
CorePath = corePath,
AffiliateId = session.AffiliateID,
Keywords = keywords
};
_referralInformation.AddOrUpdate(dictionaryKey, info, (key, oldValue) =>
{
oldValue.Count++;
return oldValue;
});
break;
}
}
}
}
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
lock (_lockRecordingObject)
{
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
SearchEngineKeywordRepository repository = new SearchEngineKeywordRepository();
List<KeyValuePair<string, SearchEngineOptimizationInfo>> currentInfo = _referralInformation.ToList();
Action logData = () =>
{
foreach (var item in currentInfo)
repository.LogKeyword(item.Value);
};
Thread logThread = new Thread(new ThreadStart(logData));
logThread.Start();
_lastRecordingDate = DateTime.Now;
_referralInformation.Clear();
}
}
}
}
EDIT: Updated Real Object
public class SearchEngineKeywordRepository
{
public virtual void LogKeyword(SearchEngineOptimizationInfo keywordInfo)
{
LogSearchEngineKeywords procedure = new LogSearchEngineKeywords();
procedure.Execute(keywordInfo.CorePath, keywordInfo.AffiliateId, keywordInfo.Keywords, keywordInfo.Count);
}
}
The general pattern being that I want to do this 'something' only every hour (in the context of a website application that gets a lot of traffic). I would breakpoint my first if statement, and then step the next line to execute inside the second if statement. When doing so, the act of initializing the SomeObject
instance would cause a null reference exception. It had a completely 100% default constructor - I didn't even specify one.
However, when I let the code go through naturally, it would execute without problem. For some reason, it seems that when I skipped over the lock call into the critical section to just test run that code, it caused all kinds of errors.
I'm curious to know why that is; I understand the lock
keyword is just syntactic sugar for a Monitor.Enter(o)
try / finally block, but that seems to be that when invoking the constructor, something else was happening.
Anyone have any ideas?
EDIT: I've added the actual code to this. I'm able to reproduce this at will, but I still don't understand why this is happening. I've tried copying this code to another solution and the problem does not seem to occur.
如果你对这篇内容有疑问,欢迎到本站社区发帖提问 参与讨论,获取更多帮助,或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱,如果其他用户或者作者回复了您的评论,将不能在第一时间通知您!
发布评论
评论(1)
我试图重现你的情况,但正如我所料,我不能。我已经在 32 位和 64 位模式下尝试了 2.0 和 4.0 运行时(调试有时在 x64 下的行为有所不同)。
显示的代码是否经过简化?你检查过你所有的假设吗?我知道您跳过了 3 行代码,包括 if 语句和锁?在这种情况下,即使将锁定对象设置为 null 也不会导致您描述的异常。
(将
_lockRecordingObject
设置为 null 会在离开lock
范围时导致ArgumentNullException
)I've tried to reproduce your situation, but as I expected I could not. I've tried both the 2.0 and 4.0 runtime, in 32 and 64 bit mode (debugging sometimes behaves differently under x64).
Is the code shown a simplification? Have you checked all your assumptions? I understand you're skipping 3 lines of code, both the if statements and the lock? In that case, even setting the lock object to null does not cause the exception you describe.
(Having
_lockRecordingObject
set to null causes anArgumentNullException
when leaving thelock
scope)